Method and apparatus for casting of non-ferrous metals

ABSTRACT

The current invention replaces the toggle clamping mechanism of known die casting machines with a hydraulic clamping mechanism. Advantageously, the machine with hydraulic clamps requires less space than the machines utilizing toggle clamping mechanisms. The machine of this invention has a significantly smaller footprint, takes up less space and is about 30% shorter than machines with toggle clamps. The hydraulic clamping mechanism of the current invention not only decreases the size of the casting machine, but also produces uniform clamping force. The hydraulic clamp according to one presently preferred embodiment of this invention is a hydro-mechanical clamp.

[0001] This claims the benefit of U.S. Provisional Patent Application Serial No. 60/330,655, filed Oct. 26, 2001 and hereby incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

[0002] The present invention relates to casting products, and more particularly to a method and apparatus for effectively and efficiently casting from non-ferrous metals such as aluminum and magnesium.

[0003] Die casting machines include two die carrying platens. One of the die carrying platens is stationary and is connected to the injection unit which injects the non-ferrous metal into the die cavity. The other of the die carrying platens is a movable platen which is moved into engagement with and clamped to the stationary platen to engage the two die halves and receive and form the metal during the casting process. The movable platen is moved out of engagement with the stationary platen so that the completed part may be removed from the dies.

[0004] Casting of non-ferrous metals is currently performed utilizing a die casting machine with a toggle clamping structure as is known in the art. Toggle clamps are utilized to join mating dies and to resist the forces created by the high pressure injection of non-ferrous metals into the cavities in the mating dies.

[0005] Toggle clamps for die casting of non-ferrous metals typically comprise four over center knuckles which apply clamping force to the four corners of the movable platen of the die casting machine. Typically, one clamp is located on each corner of the die casting machine. The mechanical nature of the clamps and the structure of an individual die can lead to unequal force application at the four corners of the movable platen to which one of the dies is attached. Die designers must balance part placement within the die to avoid exacerbating the problem of unequal force application. Furthermore, the toggle clamping structure currently utilized in die casting machines substantially increases the footprint of the casting machine.

[0006] What is needed in the art is a method and an apparatus which allows non-ferrous metal casting to be accomplished in an efficient and consistent manner while utilizing machines of smaller size than known die casting machines and which produces uniform clamping force on the die carrying platens.

SUMMARY OF THE INVENTION

[0007] The present invention provides an improved method and apparatus for use in non-ferrous casting or molding. The present invention provides a machine smaller in size than the previously utilized die casting machines for non-ferrous metal casting. Moreover, this invention provides a machine which produces equal clamping force on all four corners of the movable platen.

[0008] In one embodiment, the current invention replaces the toggle clamping mechanism of known die casting machines with a hydraulic clamping mechanism. Advantageously, the machine with hydraulic clamps requires less space than the machines utilizing toggle clamping mechanisms. The machine of this invention has a significantly smaller footprint, takes up less space and is about 30% shorter than machines with toggle clamps. The hydraulic clamping mechanism of this embodiment of the current invention not only decreases the size of the casting machine, but also produces uniform clamping force. The hydraulic clamp according to one presently preferred embodiment of this invention is a hydro-mechanical clamp.

[0009] The invention, in one form comprises a die casting machine having a hydro-mechanical clamping apparatus. In an exemplary embodiment of the current invention, the hydro-mechanical clamping apparatus comprises four retractable tie bars affixed to a movable platen. The retractable tie bars include distal tie bar lugs which are engaged by a rotary locking mechanism when the movable platen is moved into contact with the stationary platen. The rotary locking mechanism locks each tie bar to a hydraulically actuated piston. Pressure is applied to the hydraulically actuated piston to tension the retractable tie bars and clamp the movable platen to the stationary platen.

[0010] An advantage of the present invention according to this embodiment is the uniform clamping pressures supplied by the hydro-mechanical clamping mechanism. Additionally, the machine has fewer moving parts offering less repair, maintenance, downtime and quicker, more efficient and economical rebuild of the machine.

[0011] Another advantage of the present invention is the ability to provide increased tie bar, tool and die life due to superb low mold protection, uniform clamping pressure which eliminates die twisting and other problems that decrease die longevity as well as use of improved, stronger alloys. Moreover, the tie bars can be automatically balanced and the platens automatically squared.

[0012] A further advantage of the present invention is the ease of mold changeover due to the increased die access area (increased on the order of 15-20%) produced by the retractable tie bar clamping mechanism of the present invention. This increased area also allows for larger tooling.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention itself will be better understood by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawings, wherein:

[0014]FIG. 1 is a side elevational view of a casting machine according to one embodiment of the current invention;

[0015]FIG. 2 is a top plan view thereof;

[0016]FIG. 3 is a partial sectional view of the metal injection unit;

[0017]FIG. 4 is a partial sectional view of an alternative embodiment of a non-ferrous metal injection unit;

[0018]FIG. 5 is a side elevational view partially in section of a die casting machine according to one embodiment of the current invention;

[0019]FIG. 6 is an end elevational view of the movable platen; and

[0020]FIG. 7 is a sectional view of the tie bar locking mechanism.

[0021] Corresponding reference characters indicate corresponding parts throughout the several views. The description set out herein illustrates presently preferred embodiments of the invention, in one form, and such description is not to be construed as limiting the scope of the invention in any manner.

DETAILED DESCRIPTION OF THE INVENTION

[0022] Referring now to the drawings and particularly to FIG. 1, a die casting machine 30 includes a base 22, metal injection unit 26, stationary platen 14 and movable platen 12. Machine 30 is generally formed of clamp end 100 and shot end 102. Shot end 102 is of the type generally utilized in die casting machines, while clamp end 100 is of a type commonly utilized in injection molding machines. Machine 30 is formed as a hybrid of, e.g., TIS-HPM die casting machine model M-900-A, and TIS-HPM NEXT WAVE 800 ton injection molding machine. Stationary platen 14 and movable platen 12 carry die halves 32. Machine 30 includes accumulators 18 and intensifier 16 as is known in the art. Retractable tie bars 28 are affixed to movable platen 12 and are engageable in locking units 20. Movable covers (not shown) may be added to the machine 30 to protect and cover each of the retractable tie bars 28 from debris, dust, dirt and the like and prevent them and their operation from being fouled during casting operations. Movable door 24 selectively limits access to the die area of machine 30.

[0023]FIG. 2 illustrates machine 30 including retractable tie bars 28 and movable platen shuttle cylinders 34. Movable platen shuttle cylinders 34 are diagonally opposed and thus provide increased access to dies 32. As illustrated in FIG. 6, stationary platen 14 includes four rotary locking bushings 38 while movable platen 12 includes four retractable tie bars 28 affixed at one end of movable platen 12.

[0024] Retractable tie bars 28 each are received into a rotary locking bushing 38 when movable platen 12 is moved into position to engage stationary platen 14 and operatively join dies 32. Rotary locking bushing 38 is rotated and locks the respective retractable tie bar 28 in engagement with a matching lug 40.

[0025] Tie bar lugs 78 each include four lobes which pass through channels 90 of rotary locking bushings 38. After entry of the four lobes on each tie bar lug 78 through channels 90, rotary locking bushing 38 is rotated 45° so that the partial flanges located between channels 90 engage the lobes of tie bar lugs 78 and thereby retain retractable tie bars 28. While the invention shown in FIG. 6 and described herein has four lobes, other arrangements and configurations are readily encompassed within this invention. For example, each tie bar may have a series of lugs at the distal end of the tie bar and another series spaced longitudinally on the tie bar from the distal end.

[0026] Levers 86 are operably affixed to rotary locking bushings 38 as illustrated in FIG. 6. Levers 86 are hingedly connected to respective linkages 84 which are operably connected to locking cylinders 82 via pistons 88. Locking cylinders 82 are operable to actuate pistons 88 which results in substantially vertical movement of linkages 84 and rotation of levers 86 and rotary locking bushings 38. In this way, locking cylinders 82 may be utilized to rotate locking bushings 38 and thereby lock and unlock retractable tie bars 28.

[0027] Matching lug 40 is connected to hydraulic piston 44 and, when retractable tie bars 28 are locked, pressurized hydraulic fluid is supplied to face 92 of hydraulic clamp piston 44 from a hydraulic fluid source (not shown). The hydraulic fluid places matching lug 40, rotary locking bushing 38 and retractable tie bar 28 in tension and clamps movable platen 12 to stationary platen 14. Since the hydraulic clamping cylinders are located on stationery platen 14 they can be supplied with hydraulic fluid through rigid pipes, avoiding the need for flexible or moving hydraulic hoses. In one exemplary embodiment, each clamping cylinder has a transducer that monitors pressure. If a pressure drop is detected, the system tries to compensate to prevent uneven tie bar loading. If the system can not compensate, the machine will shut down and diagnose the problem. While the clamping mechanism of the current invention has been described as a hydro-mechanical clamping mechanism utilizing retractable tie bars, other hydraulic clamping mechanisms, such as those used in straight hydraulic injection molding machines, may be utilized in accordance with the present invention.

[0028] As illustrated in FIG. 3, non-ferrous metal injection unit 26 is affixed to stationary platen 14 and provides the non-ferrous material to dies 32. Shot sleeve 50 includes injection port 46 into which non-ferrous metal is inserted. Plunger 52 contacts the material inserted into shot sleeve 50 and is utilized to introduce the material into cavity 60 formed by dies 32. Plunger 52 is affixed to piston rod 54 while piston rod 54 is affixed to piston 56. In operation, piston 56 is actuated by pressurized hydraulic fluid in chamber 62 thereby causing movement of plunger 52 to inject material 58 into die 32. According to various embodiments of this invention, the material 58 to be injected may be a solid metal, sem-solid metal, a metal slug, metal slurry, liquid metal or metal of another consistency or form. If desired, a vacuum can be utilized to remove air from die 32 and assist in filling the die with the material 58.

[0029]FIG. 4 illustrates a further embodiment of non-ferrous metal injection unit 26. The non-ferrous metal injection unit 26 illustrated in FIG. 4 includes plunger 52 affixed to end 53 of piston rod 54 which is affixed to piston 56. Piston 56 is further connected to stroke adjustment screw 48. Stroke adjustment screw 48 may be advantageously utilized to adjust the stroke length of plunger 52 depending upon the current application. Stroke adjustment screw 48 is contained within stroke adjustment housing 64. Check valve 72 includes spring 74 and spring retainer 76. Guide plate 66 is affixed between packing shim 68 and packing retainer 70 and is useful for guiding piston rod 54.

[0030] After a forming operation has taken place, retractable tie bars 28 are unlocked and retract with movable platen 12. As the mold opens, retractable tie bars 28 move back out of the way and allow for quick, easy and possibly automated mold changes as well as fast and easy removal of large parts. After the parts are removed, movable platen 12 is returned to operable molding position, with each tie bar lug 78 engaged by rotary locking bushing 38, and hydraulic piston 44 supplying tension thereto.

[0031] Other die-casting clamping mechanisms are contemplated within the scope of this invention. For example, clamping pins and a locking mechanism such as that disclosed in U.S. Pat. No. 5,776,516 (hereby incorporated by reference) could be utilized for die-casting operations according to this invention. Likewise, the clamping mechanisms disclosed in U.S. Pat. Nos. 4,708,625; 6,120,724; and 6,231,329 (each of which are hereby incorporated by reference) could be utilized for die-casting operations within this invention.

[0032] While this invention has been described as having a preferred design, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. For example and without limitation, the present invention has been shown and described with respect to a horizontal injection process but it can be readily utilized in a vertical injection process of the type readily known to those skilled in this art. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fail within the limits of the appended claims. 

What is claimed is:
 1. A method of forming a part from non-ferrous metal, comprising: clamping a pair of die halves together with hydraulic force to form a die cavity; and injecting a non-ferrous metal into said die cavity.
 2. The method of claim 1, wherein said step of clamping a pair of die halves together with hydraulic force comprises clamping a pair of die halves together with hydro-mechanical force.
 3. An apparatus for forming non-ferrous metal into parts, comprising: a clamp end comprising: (a) a movable platen having a die half affixed thereto; (b) a stationary platen having a second die half affixed thereto; (c) hydraulic means for engaging said platens and said die halves to form a die cavity; a shot end comprising: (a) a shot sleeve for receiving a slug of non-ferrous metal; and (b) injection means for injecting said non-ferrous metal into said die cavity.
 4. The apparatus as recited in claim 3, wherein said hydraulic means for engaging comprises a hydraulic cylinder.
 5. The apparatus as recited in claim 3, wherein said hydraulic means for engaging comprises a hydro-mechanical connection.
 6. The apparatus as recited in claim 5, wherein said hydro-mechanical connection comprises: a plurality of retractable tie bars affixed to said movable platen; a locking means for locking said retractable tie bars to a plurality of hydraulic cylinders; and hydraulic pressure providing means for applying hydraulic pressure to said hydraulic cylinder and thereby placing said retractable tie bars in tension. 